Bed plate for duplicating machines



Dec. 3l, 1935. 1 W, HERNLUND 2,026,037

BED PLATE FOR DUPLIGATING MACHINES Filed Aug. 13, 1934 jmmeg.

Patented Dec. 31, 1935 UNTTED STATES John W. Hernlund, La Grange, Ill., assigner to Ditto, Incorporated, Chicago, Ill., a corporation of West Virginia Application August 13, 1934, Serial No. 739,597

4 Claims.

'I'his invention relates to bed plates for duplicating machines and `has for its object the provision of a new and improved bed plate of this character which uses aluminum as a base metal.

5 The improved bed plate as constructed in accordance with the process outlined herein, is stiffer in its final form than ordinary aluminum, has a harder surface and will not discolor the gelatin band used in the duplicating machine such as would be the case if the aluminum were not prepared and treated in the manner hereinafter set forth.

The bed plate must present a backing for the gelatin band which shall be quite straight so that the backing for the gelatin band lies substantially in one plane. This, however, is to be construed with the necessity of providing suitable means to prevent the back of the gelatin band from adhering too closely to the surface of the bed plate for which purpose the surface is 'provided with a plurality of dot-like humps. -These dot-like humps are suitably distributed over the entire active face of the bed plate, meaning by the term active face that portion thereof which serves as the backing for the gelatin band. The opposite ends of the plate are suitably bent to serve both for holding and :stiffening purposes and also to provide a rounded surface over which the gelatin band may slide.

A preferred embodiment of the invention is described more in detail by referring to the accompanying drawing in which:

Fig. 1 is a top plan View of the improved bed plate.

Fig. 2 is a bo'ttom plan View of the improved bed plate.

Fig. 3 is an enlarged partial sectional View thereof on line 3 3 Fig. 1.

`Fig. 4 is an enlarged partial longitudinal section thereof on line 4 4 of Fig. 1.

As apparent from the drawing, the bed plate consists of a sheet of aluminum having a flat portion I, and the turned in extremities ll and l2. A plurality of dot-like humps I3 are punched upwardly out of the body of the material so that they constitute small pellets of that material, that have been slightly displaced out, of the plane of the material. This punching operation is performer by a punch which punches two or three transverse rows, and this punch is then moved longitudinally of the plate to complete the formation of said humps throughout the entire active surface. Such punching operation leaves the plate in a curved condition with the active surface convex. The plate is then straightened in any (Cl. lOl- 131) suitable manner. Suitable holes I4, are also provided in the plate so that it may be properly attached to the frame work of the machine.

After the plate has een suitably straightened it is treated by an anodic process, one form of 5 such process being known in the art as the alumiliteprocess. In accordance with this process the plate is first treated with benzine and is then suitably treated by a hot solution of a suitable cleaner for a time period of probably 10 from fifteen to fifty minutes. vThe plate is then immersed in an electrolytic bath, having a sulphuric acid or chromic acid solution, the plate serving as an anode in the bath, and the lead lining of the plate serving as cathode. This 15 treatment is continued for a certain length of time by virtue of which a film is formed on the plate which may be from one to one and one-half thousandths of ail-inch thick and'is probably in the nature of an aluminum hydroxide. .2o

The treatment in the electrolytic bath is carried on under a current density of approximately twenty amperes per square foot. The plate with the said coating may then be left to age and the film, or coating, would in about twoA Weeks 25 change to aluminum oxide; but this aging process may be hastened by immersing the plate in a suitable hot liquid. The coating that is thus formed on the surface seems to have the characteristics of a glazing. It is extremely hard 30 and it prevents the aluminum plate from discoloring the gelatin band such as used in duplicating machines. Such discoloration 'must be avoided as the gelatin band is frequently wound and unwound from a pair of rolls, and the dis- 35 colored backing would thus contact the printing surface of the gelatin band and bring about harmful discoloration thereof.

Having thus described one form of the invention, what is claimed as new and desired to be 40 secured by Letters Patent is:

1. The process of preparing a bed plate for duplicating machines of the hectograph type which consists in producing throughout the active surface of an aluminum plate an irregular 45 surface composed of dot-like humps whereby the said plate is rendered concave, straightening said plate, and thereafter subjecting said plate to an anodic coating process whereby to provide a coating on the same of an aluminum oxide, 50 whereby said plate permits the free movement of a gelatin pad thereover without discoloration.

2. The process of preparing a bed plate for duplicating machines of the hectograph type which consists in producing throughout the ac- 55 tive surface of an aluminum plate an irregular surface composed of dot-like humps, and thereafter subjecting said plate to an anodic coating process whereby to provide a coating on the same of an aluminum oxide, whereby said plate permits the free movement of a gelatin pad thereover without discoloration.

3. As an article of manufacture, a bed plate for duplicating machines of the hectograph type which consists of a flat plate of aluminum having dot-like projections on its active surface and having on said active surface a coating consisting of a continuous deposit of anodic aluminum oxide, whereby said plate permits the contact of a gelatin pad therewith without discoloration.

4. As an article of manufacture, a bed plate for duplicating machines which consists of a flat plate of aluminum having dot-like projections on its active surface and having on said active surface a coating consisting of a continuous deposit of anodic aluminum oxide having a. thickness of one to one and one-half thousandths of 10 an inch.

JOHN W. HERNLUND. 

